Table 4. Analysis of variances for the fitted regression model.

Source	df	Sum of squares	Mean squares	F-value	P-value	Significance level
Regression	9	230.247	25.5830	67.12	<0.0001	**
Linear	3	193.084	64.3614	168.87	<0.0001	**
Square	3	33.808	11.2694	29.57	0.001	**
Interaction	3	3.355	1.1182	22.9	0.138
Lack of fit	3	1.687	0.5623	5.14	0.167
Pure error	2	0.219	0.1094
Total	14	232.152			R2 = 0.9918

*P<0.05, **P<0.01.